Group III-V materials (e.g., AlN, GaN, and InN) are suitable materials for fabrication of a variety of semiconductor devices. For example, gallium nitride (GaN) and other III-nitride materials have relatively wide band gaps and can be used to make electro-optic devices (e.g., light-emitting diodes (LEDs), laser diodes (LDs), etc.) that emit radiation in the green and blue regions of the visible spectrum. Group III nitride materials can also be used to fabricate high-power electronics because they exhibit higher breakdown voltages when used for fabricating integrated transistors.
Because high-quality substrates of III-V materials may be difficult to obtain, a group III-V material may typically be heteroepitaxially grown on a foreign substrate of a different material. For example, GaN may be grown on a sapphire substrate. However, large lattice mismatches may exist between the foreign substrate and epitaxial layers of the III-V material and may lead to formation of threading dislocations. This may deteriorate the quality of the semiconductor devices formed using the III-V material.